Tank Sight Glass DIN 28121 - PN10 | PN25 | ACI Industriearmaturen GmbH

Circular Sight Glass DIN28121 - assembly for bolting straight onto DIN flanges

Short description - sight glass fitting DIN28121 for flanges PN10 or PN25

The ACI screw-on tank sight glass Type 321 according to DIN 28121 includes a PTFE-enclosed resilient gasket as inner seal. This gasket is installed in off load contact, with the metal flanges completely surrounding the edge of the glass disc, providing excellent protection.

Type 321 is delivered in assembled condition ready to be mounted onto a carrier flange according to DIN EN 1092-1. In the unlikely case of glass damage during normal operation, Type 321 can be exchanged quickly and without special tools.

The sealing in the force shunt prevents the seals from being loosened, which means that it is no longer necessary to tighten the clamping screws on site.

The PTFE enclosed gasket makes Type 321 especially suited for use with food, acids, alkaline solutions, and most corrosive chemicals. For the glass disc itself, we offer protective sheets made from mica, PCTFE or FEP to protect the glass surface from most harmful influences.

Accessories like our wipers type SW1, spray nozzles SVI or lights are also available for delivery directly from us.

For the flanges, you can choose from our range of high quality stainless steel, including 1.4541, 1.4404 and 1.4571. or any steel type fitting your specifications. For processes with low corrosion risks, we can also offer low-grade pressure vessel steel alloys like P265GH or S235JRG2. As glass discs, we exclusively use industrially proven MAXOS® borosilicate glass according to the established standard DIN 7080.

Read on for more technical information or watch our product video in the top!

Technical details


Base flange:
1.4404 / 1.4539 /1.4571 / 1.4541 / 2.4602 / 2.4605 / other materials on request

Cover flange:
1.4404 / 1.4539 /1.4571 / 1.4541 / 2.4602 / 2.4605 / other materials on request

Sight glass:
Borosilicatglass DIN 7080


DIN 28121

Nominal size:

DN40 up to DN200

Nominal pressure:

PN10 or PN25 / for higher pressures see type 322


Max. 200 ° C for higher temperatures see type 323


PTFE-enclosed resilient gasket (max. 200°C)

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Tank Sight Glass DIN 28121 - PN10 | PN25